Interestingly, when your European (now) wife entered the US, were you planning on marrying at the time? And if so, did she indicate on her visa application that she was planning on getting married? there is a question on the visitors visa form to which you must answer 'No' regarding plans of marriage, or you won't get a visitors visa. However if you enter a country with the intent of marrying, but answer 'no' to said question, you can be accused (and have to prove otherwise) of violating immigration policy by not telling the truth on the visitor visa. And if you have lied on a visa application, you can be banned for 10 years.
My wife entered the US via Visa Waiver Program. No questions asked regarding intent to marry. If you plan on getting married and you require a visa, you will require a fiancé visa (which can take quite a while to obtain).